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Author notes

He is author of two books in environment history, Conservation and the Gospel of Efficiency; the Progressive Conservation Movement, 1890–1920 (Harvard University Press, 1959) and, in collaboration with Barbara D. Hays, Beauty, Healthy and Permanence; Environmental Politics in the United States, 1955–1985 (Cambridge University Press, 1987) as well as seventy articles and chapters on varied environmental history subjects.